Polymer, resist composition and patterning process

Abstract

A polymer comprising recurring units of formulae (1) and (2) wherein R 1 and R 3 are H or methyl, R 2 and R 4 are C 1-15 alkyl, R 5 to R 8 are H, or R 5 and R 7 , and R 6 and R 8 form trimethylene or 1,3-cyclopentylene and having a Mw of 1,000-500,000 is novel. A resist composition comprising the polymer as a base resin is sensitive to high-energy radiation, has excellent sensitivity, resolution and etching resistance and lends itself to micropatterning with electron beams or deep-UV.

What is claimed is:  
     
       1. A polymer comprising recurring units of the general formula (1) and recurring units of the general formula (2) and having a weight average molecular weight of 1,000 to 500,000,                   
       wherein R 1  and R 3  each are hydrogen or methyl, R 2  and R 4  each are a straight, branched or cyclic alkyl group of 1 to 15 carbon atoms, R 5 , R 6 , R 7  and R 8  each are hydrogen, or a pair of R 5  and R 7  and a pair of R 6  and R 8  each stand for a group of atoms to form trimethylene or 1,3-cyclopentylene. 
     
     
       2. The polymer of  claim 1  further comprising recurring units of the general formula (3):                    
       wherein R 9  is hydrogen or methyl, R 10  is hydrogen or a straight, branched or cyclic alkyl group of 1 to 15 carbon atoms, R 11  is hydrogen or CO 2 R 12 , R 12  is a straight, branched or cyclic alkyl group having 1 to 15 carbon atoms in which at least one oxygen atom may intervene in any carbon-to-carbon bond, and X is methylene or an oxygen atom. 
     
     
       3. A resist composition comprising the polymer of  claim 1  as a base resin. 
     
     
       4. A process for forming a resist pattern comprising the steps of: 
       applying the resist composition of  claim 3  onto a substrate to form a coating,  
       heat treating the coating and then exposing it to high-energy radiation or electron beam through a photo mask, and  
       optionally heat treating the exposed coating and developing it with a developer.